This application claims the priority of 198 18 863.3, filed Apr. 28, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a selection system for an automatic motor vehicle transmission, and more particularly, to a selection system comprising selector element configured to be manually adjustable to different positions for selecting transmission adjustments, a locking system having a controlled actuator arrangement for automatic locking and unlocking of the selector element in at least one defined position (P, N) as a function of defined operating conditions.
The invention further relates to all types of automatic transmissions, for example, fully automatic and partially automatic gear boxes. In addition, so-called automatic converter step mechanisms and variable transmissions with infinitely variable transmission ratios with or without gears are also contemplated.
One such known selection system is described in DE-196 41 706 C1. The selector element is a swivellably disposed selector lever which can be swivelled from a parking position P by way of a reversing position R into a neutral position or idling position N, in which the torque transmitting of the vehicle transmission is interrupted, and into at least one forward driving position D.
For positions P and N, locks are provided which act as a function of certain operating conditions. In the parking position P, a locking of the selector lever is required as long as the vehicle brake is not operated and the ignition key is not situated in the ignition lock (or the ignition is not switched on). As soon as the ignition key is situated in the ignition lock (or the ignition is switched on) and the brake is operated, the selector lever is to be released. In the following description, this function will be called a P-lock. For operation of the selector lever from the neutral position N into the reversing position R, a lock is also provided which is to be active as long as the vehicle has not yet fallen below a defined limit speed. In the following description, this function will be called an R-lock. However, an operation of the selector lever from D to N, however, must not be hindered by these locks. These functions are carried out as described in DE-196 41 706 C1.
DE 196 01 442 C2 discloses an arrangement in which locking systems of the selector lever, which are assigned to the parking position P and the reversing position R, can be unlocked by exciting a solenoid. The locking function is generated by spring force. In this known selector lever lock, the armature has pin-type locking members on its axial ends. These locking members engage in bores on web flanges of the selector lever for the purpose of locking.
The actuators or control elements, which bring the above-mentioned locking devices into the locking and the unlocking position, are preferably electromagnetic control elements and springs but may also be other elements, such as hydraulically or pneumatically operated elements. It should not be possible to unlock the locks at the selector element by a driver's manual operating force, if the operating conditions which are required for an unlocking do not exist; for example, without a driving authorization of the driver; unless the ignition key is in the ignition lock; the vehicle brake is activated; when a vehicle break lock is not unlocked; and/or if the vehicle speed is below or above a defined limit value.
A control element must, however, also be able to unlock the lock if the corresponding operating conditions have been met but the driver has exercised a manual operating force on the selector element before these operating conditions have been met. In this situation, there is the risk that the mechanical locking elements are compressed so much by the manual operating force on the selector lever that they can no longer be separated by a control element or that the control element would have to be unacceptably large with respect to the required space and weight or because of the resultant higher operating heat by a larger electromagnetic control element.